Recently, many countries build their high speed rail systems. In a high speed rail system, the typical speed of train is as high as 350 km/hr. The high speed trains are used to serve users for long distance travelling. For example, passengers may travel between countries in Europe, between provinces in China, and so on. It will be an attractive service to provide communication services, which allow users can browse the Internet, watching on-line videos, processing e-mails in the high speed rail.
In LTE-A standard working group, the mobile relay technique is discussed to support the high speed rail scenario. The scenario is shown in FIG. 1A. Mobile relays can be equipped in every carriage or in several carriages of a train. Users can connect to the mobile relay near to them. The mobile relay plays roles as an eNB for users. Mobile relay redirects the received data from users to the donor eNB (DeNB) deploying along the train route. On the other hand, the mobile relay also distributes the data from the network to users.
However, in the above scenario, the train go through base stations along the train route in a high speed, and all mobile relays will perform handover procedures one-by-one in short intervals. Therefore, it is important to design a very quick and still yet reliable handover scheme so as to allow users to communication services in a high speed rail.